Water Bill in Grasfontein

I have a bad experience with City of Tshwane since more than 10years, first started with a bill of water for a month to a total of R50 000, a house occupied by 2 people, when inquiring was told I have a leakage, called up plumbers using my own money, nothing was found in my yard, reported the matter and was informed they are busy with investigation and I should countiue pay what I was paying while busy with investigation till today nothing from them and my water bill has gone up to more than R500 000, don’t know how possible two people leaving in a house could use that much water. Hope someone can advise me. Thanks